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Provisions for Adequate Combustion and Ventilation Air
WARNING: This heater shall not be installed in
a confined space or unusually tight construc-
tion unless provisions are provided for adequate
combustion and ventilation air.
Today’s homes are built more energy efficient than ever. New
materials, increased insulation and new construction methods
help reduce heat loss in homes. Home owners weather strip
and caulk around windows and doors to keep the cold air out
and the warm air in. During heating months, home owners
want their homes as airtight as possible.
While it is good to make your home energy efficient, you need
fresh air. All fuel-burning appliances need fresh air for proper
combustion.
Supplying Adequate Ventilation
This appliance must be installed in an unconfined space.
The following information will help you classify your space and
provide adequate ventilation for complete combustion.
An Unconfined Space
has a minimum volume of 50 cubic
feet for each 1000 BTU/Hr input rating of all appliances in the
space. (4.8 M
3
per kw), (cubic feet equals length x width x
height of space).
A Confined Space
has a volume of less than 50 cubic feet for
each 1000 BTU/Hr input rating of all appliances in the space,
(4.8M
3
per kw), (cubic feet equals length x width x height of
space).
Determining if You Have a Confined or Un-
confined Space
Use this worksheet to determine if you have a confined or
unconfined space.
Space: Includes the room in which you will install heater plus
any adjoining rooms with doorless passageways or ventilation
grills between the rooms.
1. Determine the volume of the space (length x width x height).
Length x Width x Height = _____cu. ft. (volume of space)
Example: Space size 25’ (length) x 25’ (width) x 8’ (ceiling
height) = 5,000 cu. ft. (volume of space)
If additional ventilation from adjoining room(s) is supplied
with grills or doorless openings, add the volume of these
rooms to compute the total volume of the applicable space.
2. Divide the space volume by 50 cubic feet to determine the
maximum BTU/Hr the space can support.
________(volume of space) ÷ 50 cu. ft. = (Maximum BTU/
Hr the space can support.
Example: 5,000 cu. ft. (volume of space) ÷ 50 cu. ft. = 100
or 100,000 (maximum BTU/Hr the space can support)
3. Add the BTU/Hr of all gas burning appliances in the space.
Gas range BTU/Hr
Vented gas heater BTU/Hr
Gas fireplace logs BTU/Hr
Other gas appliances* +
BTU/Hr
Total = BTU/Hr
Example: Gas range 60,000 BTU/Hr
Vent-free logs +
29,000 BTU/Hr
Total = 89,000 BTU/Hr
*Do not include direct-vent gas appliances. Direct-vent draws
combustion air from the outdoors and vents to the outdoors.
4. Compare the maximum BTU/Hr the space can support with
the actual amount of BTU/Hr used.
__________ BTU/Hr (maximum the space can support)
__________ BTU/Hr (actual amount of BTU/Hr used)
Example: 100,000 BTU/Hr (max. the space can support)
89,000 BTU/Hr (actual amount of BTU/Hr used)
The space in the above example is an unconfined space
because the actual BTU/Hr used is less than the maximum
BTU/Hr the space can support. If the space had been confined,
your options would be as follows:
A. Rework worksheet, adding the space of an adjoining
room. If the extra space provides an unconfined space,
remove door to adjoining room or add ventilation grills
between rooms. See Ventilation Air From Inside Build
-
ing.
B. Install a lower BTU/Hr heater, if lower BTU/Hr size
makes room unconfined.
Converting Confined Space to Unconfined
Space
Additional volume to convert a confined to an unconfined space
could come from an adjoining space. When using an adjoining
space, you can provide two permanent openings: one within
12” of the ceiling and one within 12” of the floor on the wall
connecting the two spaces (see options 1 and 3, Figure 2), or
remove the door into the adjoining room.
Ventilation Air From Outdoors for Unusually
Tight Construction
WARNING: If the area in which the heater may be oper-
ated is smaller than that defined as an unconfined space
or if the building is of unusually tight construction, provide
adequate combustion and ventilation air by one of the
methods described in the National Fuel Gas Code, ANSI
Z223.1/NFPA 54, Section 5.3 or applicable local codes.
Unusually tight construction is defined as construction
where:
a. walls and ceilings exposed to the outside atmosphere have
a continuous water vapor retarder with a rating of one perm
(6 X 10.
11
kg per pa-sec-m
2
) or less with openings gasketed
or sealed and
b. weather stripping has been added on openable windows
and doors and
c. caulking or sealants are applied to areas such as joints
around window and door frames, between sole plates and
floors, between wall-ceiling joints, between wall panels, at
penetrations for plumbing, electrical and gas lines and at
other openings.
If your home meets all of the three criteria above, you must
provide additional fresh air.
You may provide two permanent openings: one within 12” of
the ceiling and one within 12” of the floor. Connect these items
directly to the outdoors or spaces open to the outdoors. These
spaces include attics and crawl spaces. Follow the National
Fuel Gas Code NFPA 54/ANSI Z223.1, Section 5.3, Air for
Combustion and Ventilation for required size of ventilation grills
or ducts.
IMPORTANT:
Do not provide openings for inlet or outlet air into
attic if attic has a thermostat-controlled power vent. Heated air
entering the attic will activate the power vent.